1. Field of the Invention
The invention pertains primarily to the field of transmission of short pulse microwave signals, and more specifically the synchronization of these short pulse radiated signals from an array of solid state or other triggerable transmitters.
2. Description of the Prior Art
Combining or processing networks for efficiently combining coherent electromagnetic energy and focusing in the far field are essential for transmitting signals of very short pulse duration. They are of interest when these signals must be synchronized to yield a maximum signal incident on a selected target area or target in space. Generally, combining networks of the past have not had the capabilities of efficient operation over the subnanosecond duration required.
U.S. Pat. No. 3,714,655 entitled "Array Antenna Processing System" pertains to microwave transmission line coupling networks or matrices to receive signals from an antenna array. An output pulse is generated which represents "a substantially perfect summation of the total energy of the plurality of effectively discrete sources." This scheme is applicable to both receiving and transmitting applications. However the short term jitter and long term (thermal) drift present in solid state activated short pulse sources reduces the desired summation amplitude and degrades beam forming.
Another approach is the use of microcircuit switches on a gallium arsenide substrate. A high energy laser beam is radiated over the surface of the substrate causing each of the switches to break down simultaneously thereby synchronizing the pulse array, at least, at boresight. There are a number of problems with this approach. It is not energy efficient. Generally, more energy is required to break down the switches than is transmitted to a target. This results in a very costly laser and associated power supply system. Also the introduction of incremental time delays at each element necessary for steering the beam in space is required, resulting in additional hardware complexity and cost.
Other approaches use avalanche devices for beam formation and increased peak power in the far field. But these devices running without short term jitter or thermal compensation cannot control with the accuracy required; that is, to a small fraction of a microwave cycle (e.g., a number of picoseconds).
Accordingly, it is an object of the invention to provide an improved array microwave transmission system which meets the minimum absolute short term jitter and thermal drift requirements.
It is another object of the invention to provide an improved synchronization system for the array.
It is yet another object of the invention to provide an array having and an improved scanning capability.
It is still another object of the invention to provide an array having improved beam focusing capabilites.